JPS5887525A - Illuminating optical system for endoscope - Google Patents

Abstract

PURPOSE:To eliminate illumination shortage in the circumferential part of the field of view, by using an optical fiber flux which is uneven in distribution of optical fibers of the emitting end. CONSTITUTION:To the emitting end face of an illuminating light guide 2, a single fiber 5 is junctioned, and in front of the single fiber 5, a convex lens 6 is stuck. In the center part of the emitting end of the light guide 2, a rod 7 consisting of light non-transmitting metal, plastic, glass, etc. is embedded. By suitably selecting a ratio in which the rod 7 covers a circular area B of the center part, brightness of the center part and the circumferential part of the field of view are equalized.

Description

[Detailed description of the invention] It is related to the system.

As shown in FIG. 1, the conventional optical system for internal use includes a light guide 2 embedded in the distal end portion 1 of the endoscope, and the light guide F.
:'2, and a concave lens 3 fixed to the front end surface of the tip part 1 so as to be located near the output end of the lens.
In recent years, the angle of view has increased to 1 in order to widely observe the subject surface 4 such as the body wall.
Although endoscopes having observation optical systems with an angle of 00° or more have come into use, there is a problem in that an illumination optical system using a concave lens cannot brightly illuminate the periphery of the visual field. Therefore, in order to improve this rose, for example, in JP-A-56-204
An endoscope illumination optical system described in Japanese Patent No. 28 has been considered, and as shown in FIG.
A convex lens 6 is fixed to the front end surface of the distal end 1 so as to be located in front of the lens. However, even with this illumination optical system, the periphery of the field of view is limited in endoscopes with an angle of view of 120° or more. The problem was that it was still dark. That is, the principle of this illumination optical system is as shown in Fig. 3.
It can be considered that the output end 5a of is projected onto the subject surface 4 by a convex lens 6, and the light ray a that illuminates the periphery of the visual field
, a', a' are the likelihood lines from the edge of the output end [irl5a, and the light beam that illuminates the center P of the field of view is the single 7 aino ζ-5
It is a ray of light that comes out from point Q in . The reason why the point 9 is not on the output end surface 5a of the single fine lens 5 is because the convex lens 6 has a curvature of field aberration and the output end surface 5a is forward (protruding).

Furthermore, the light beam passing through the edge of the output end surface 5a is transmitted through the light guide l'
2, the area A is surrounded by two arcs as shown in FIG. 4, and the light ray passing through point Q is light guide 2
It emerges from a circular region B at the center of one output end surface 2a. Therefore, the light distribution characteristic in this case is as shown in FIG. Due to the brightness at the center, it cannot be seen until a certain amount of time is passed, and even if a small amount of illumination light actually reaches it, that part is excluded from the observable field of view. In particular, when taking photos, if you try to capture the dark areas in the periphery, the bright areas in the center will appear pure white (
If you shoot so that the center of the image is clearly visible, the peripheral areas will be too dark and appear completely black, resulting in the same result as if the lighting range was narrow (the angle of view was narrow). Put it away. A single fiber is a thick optical fiber with a core and a cladding.
It can be thought of as a thicker version of one of the optical cores used in light guides and the like.

In view of the above-mentioned problems, the present invention aims to provide an illumination optical system for interior decoration that is capable of wide-angle illumination.
Based on the embodiment shown in FIGS. 9 to 9, the same members as those in the conventional example described above are given the same reference numerals. A rod made of solid metal, plastic, glass, etc.

According to the present invention, 2Ji! Since the W illumination optical system is constructed as described above, if the light beam 7 were to memorize area B completely, the light distribution characteristics would be as shown by the solid line in FIG.
No light comes to the center of the field of vision.

However, if the rod 7 does not completely cover area B, then
The light distribution characteristics become as shown by the dotted line in Figure 7, and the brightness at the center and periphery of the field of view becomes uniform, giving the same effect as an apparent wide-angle endoscope. You will be able to see better. Also, by embedding the rod 7 in the center of the output end of the light guide 2, the output end surface 2a of the light guide 2 becomes larger, which is the same as widening the field of view, that is, widening the angle of illumination. become.

Next, in more detail, the diameter d of the rod 7 and the length of the single fiber 5 (where L is the distance from the edge of the output end surface 5a of the single-striped Aino 8-5 to the output end 11ji2a of the light guy P2) The relationship with the diameter of the fiber 5 will be described. In FIG. 8, the distance from the point Q to the output end surface 2a of the light guide 2 is defined as ω, and the maximum angle that the light beam in the single-seven eye/gun 5 makes with the optical axis O is ω. First of all, if the rod 7 enters the area A, the light weight around the field of vision will also drop, so to prevent this from happening,
2L-tanω≧d (1) is a necessary condition. Father, as a condition to prevent the cross section of the fibers of the core fibers of the light guide 2 from being reflected on the surface of the subject, Q * tan ω≧φ 9.6.0.1.
, (2) is required (where φ is the diameter of one fiber of the light guy 12). This is because point P corresponds to the image of point Q, so if light guy 12 is placed at point Q,
If the light emitting end face 2a is placed, the cross section of the fibers of the light guide 2 will be reflected on the surface of the object to be examined, making it visually appealing. Therefore, it is necessary to separate the output end surface 2a of the light guide 2 from the point Q.
If Qtanω, which is the size of the out-of-focus circle, is equal to or larger than φ, the cross section of the fiber of the light guide 2 will not be visible. In reality, there are no core particles on the optical axis and there is a rod 7, but the above concept also applies to object points on the object surface that are far from the optical axis, and even in that case, objects that are relatively close to the optical axis Equation (2) is required as a condition that the cross section of the fiber of the light guy 12 is not reflected on the point. As shown in FIG. 8, when the output end face 5a of the single fine nozzle 5 is made into a curved surface, it is better to set the following restrictions on the shape of the curved surface. That is, as shown in FIG. 9, if we consider a ray C that passes through an arbitrary point on the output end face 5a of the single fiber 5 and has the largest angle with the optical axis O in the single fiber 5, this ray C The conditions under which no total reflection occurs at the output end face 5a of the single fiber 5 are: ■ 1β1≦5in−' −−ω ・・・・・・・・・
・(3) becomes. However, 1. n is the refractive index of the core of the single fibers 5, β is the angle that the normal vector 1 of the curved surface makes with the optical axis O, and ω is the maximum angle that the normal vector 1 of the curved surface makes with the optical axis O. The curved surface is expressed by the formula (3
) is not satisfied, the output end face 5 of the single fibers-5
Total reflection of the light ray occurs at a, resulting in a loss of light rays. In reality, since the intensity of light rays that form a large angle with the optical axis O is generally weak, the condition of equation (3) may be set to be looser as shown below.

1β1≦2 (stn-'--ω) -=-・
...(4) Next, if we explain other embodiments,
FIG. 10 shows a second embodiment in which the first conventional illumination optical system in which a concave lens 3 is placed in front of the light guide 2 is combined with the first embodiment, in which the above g- is implemented. As an example, depending on how the diameter of the rod 7 is selected, it is possible to prevent the light from being completely absent at the center of the field of view as shown by the solid line in FIG. 7 by combining the above-mentioned first conventional example. FIG. 11 shows a third embodiment in which the light guide 2 is made movable in the optical axis direction within the cylindrical chamber 1a of the distal end portion 1 in the first embodiment. According to this embodiment, since the position of the rod 7 changes, the light distribution can be changed depending on the purpose. Furthermore, since the light also hits the inner surface of the cylindrical chamber 1a, it is better to make the inner surface a reflective surface.

Figure 12 shows that the convex lens 6 in the first embodiment is made up of two convex lenses 61 and 62 (the single-phi round rods attached to the front of the six lenses are not counted in the number). ) In the fourth embodiment, by increasing the number of convex lenses from one to two, the distortion of the convex lenses can be reduced, and as a result, bright illumination to the periphery of the visual field can no longer be over-the-top. . Distortion aberration in this case will be explained in detail with reference to FIG. Let point S be an object point. Since the light flux emitted from the light guide 2 is rotationally symmetrical about a straight line parallel to the optical axis 0, the chief ray E of the object point S is
It can be thought of as a ray that passes through and is parallel to the optical axis O.

Considering the distortion aberration of this chief ray E, as the distance of the chief ray E from the optical axis 0 increases, the emission angle γ of the chief ray E
increases rapidly, resulting in positive distortion. Therefore, with respect to the convex lenses 61 + 62, the light emitted from the unit area of the single fibers -5 that are conjugate with the object surface 4 is projected onto a wider object surface 4 as the distance increases, so that the screen The surrounding area of the subject surface 4 becomes dark.

To reduce positive distortion, increase the number of convex lenses. Therefore, in this fourth embodiment, two convex lenses are used. In this example, a single-fi rod is attached to the front of the convex lens 61;
Since it is difficult to achieve a sufficient waterproof effect when attaching 1 alone to the tip of an endoscope, a round rod of single fibers is pasted to the front of the convex lens 61 to increase the length of the periphery of the lens. It is designed to take a long time. If an ordinary glass plate is used instead of a single fiber string, it is undesirable because the light hits the grained portions of the side surface of the glass plate and is lost, but this problem will not occur if a single fiber is used.

In each of the above embodiments, an impermeable rod 7 is buried in the center of the output end of the light guide 2, but the distribution of optical fibers in the light guide 2 is made rough in the center and dense in the periphery. A similar effect can also be obtained by doing this. Also, instead of the single fiber 5, a metal with a reflective inner surface 2
A cylindrical reflector of ξ, which is a glass rod with a polished periphery, can be used.

The concept of the present invention can be applied not only to improving the light distribution in a wide-angle endoscope, but also to eliminating uneven illumination caused by the ξ ralux between the illumination optical system and the observation optical system. To explain this in detail, FIG. 14 shows the case where the close object surface 4 is observed using the first conventional endoscope illumination optical system, and the positions of the observation optical system and the illumination optical system are Due to the misalignment, uneven illumination occurs in the field of view of the endoscope such that the upper part is dark and the lower part is dark, as shown in FIG. The application example shown in FIG. 16 eliminates this illumination unevenness, and uses a light guide 2' in which a part of the periphery is replaced with a rod 7 in place of the light guide 2 of the first embodiment. The cross section of the output end of this light guide 2' is 17th.
As shown in the figure.

In this way, as shown in FIG. 18, the light distribution can be made brighter in the upper part of the visual field and darker in the lower part, and as a result, the visual field can be uniformly illuminated. That is, by appropriately removing a portion of the light guide r from the output end of the light guide, the light distribution can be adjusted depending on the purpose. This idea can also be used as a means to avoid the problem of the light from the light guide hitting the nozzle of the inner bowl, hood, etc. Father, Light Guide 2'
In addition to replacing a part of the periphery with a rod 7, the same effect can be obtained by using a light guy P2' with an uneven distribution of optical fibers as shown in FIG.

Next, a numerical example of the optical system of the present invention will be shown using the fourth embodiment shown in FIG. However, R1-R7 is the radius of curvature of each surface, dl % ds is the interval between each surface, and N, -N is the refractive index of each lens or the core of a single fiber.

Rd N 1 ~ 2.7 1.805182 ~
1.6 1.8833 -1.868
0.34 4 3.447 1.9 1.8835
-58.577 0.13 6 10.823 2.4 1.627
~ D=3.1 as, d=0.67m, ω=18
”, L=2.29m.

φ-0,031111, Q key, irilml, D
-2Ljan ω-1,612101°Q tanω
= maximum value of y71gpeng β -8,234°.

2(sln-'-1ω>44o, 236°.

Furthermore, N1. N6 is the refractive index of the single-fiber A- core, and the refractive index of their cladding is 152.

As described above, according to the illumination optical system for an endoscope according to the present invention, wide-angle illumination can be performed OT, and it is also possible to eliminate uneven illumination and adjust the light distribution.

[Brief explanation of the drawing]

1 and 2 are diagrams showing the second and second conventional illumination optical systems for endoscopy, respectively, FIG. 3 is a diagram showing the illumination state according to the second conventional example, and FIG. 4 is the FIG. 5 is a diagram showing the light distribution characteristics of the second conventional example, and FIG. 6 is an implementation of the illumination optical system for an endoscope according to the present invention. Figure 7 shows an example, Figure 7 shows the light distribution characteristics of the above example, Figures 8 and 9 are explanatory diagrams of the conditions of Example L, Figures 10 and 11 respectively show the light distribution characteristics of the above example. FIG. 12 is a diagram showing the optical system of the fourth embodiment, FIG. 13 is an explanatory diagram of distortion aberration of the fourth embodiment, and FIG. 14 is a diagram showing the optical system of the fourth embodiment. and FIG. 15 are diagrams showing the illumination state and endoscopic field of view according to the first conventional example, respectively;
FIG. 16 is a diagram showing the illumination state according to the application example of the present invention, FIGS. 17 and 18 are diagrams respectively showing the cross section and light distribution characteristics of the output end of the light guide of the above application example, and FIG. FIG. 6 is a diagram illustrating a cross section of an output end of a light guide according to an applied example. ■...Endoscope tip, 2...Light guide, 4...
・Subject surface, 5...Single fine angle, 6...Convex lens, 7...1-1 Figure 2 (1a21 Figure 12 Figure 13)

Claims (3)

[Claims] (1) An optical fiber bundle with an uneven distribution of optical fibers at the output end, a positive lens system placed in front of the output end, and a cylindrical lens system placed between the output end and the city lens system. An endoscope illumination optical system comprising a reflector. (2) The illumination optical system for an endoscope according to claim (1), wherein the density of the optical fibers of the optical fiber bundle is higher in the periphery than in the vicinity of the center of the output end face. (3) The illumination optical system for inner stitching according to claim (1) or (2), wherein a single fine nozzle is used for the cylindrical reflector.